Mechanisms of Self-Diffusion of Linear Associative Polymers Studied by Brownian Dynamics Simulation
Mechanisms of Self-Diffusion of Linear Associative Polymers Studied by Brownian Dynamics Simulation
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布朗动力学模拟研究线性缔合聚合物的自扩散机理
DOI：
10.1021/acs.macromol.1c01508
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发表时间：
2021
期刊：
影响因子：
5.5
通讯作者：
Olsen, Bradley D.
中科院分区：
文献类型：
--
作者：
Rao, Ameya;Ramírez, Jorge;Olsen, Bradley D.
缔合聚合物凝胶中异常的自扩散行为被归因于不同长度尺度上的多种扩散机制的存在；然而，这些动态模式在带有悬挂式粘贴的线性聚合物网络中的作用仍然未知，特别是在粘贴密度低于平均场极限的情况下。本文发展了一个广义布朗动力学模型来研究具有规则间距的无缠结线性聚合物的瞬时结合对自扩散的影响，该模型被选为具有广泛实验意义的典型缔合网络模型。这些模拟揭示了几种扩散机制之间的相互作用，包括分段波动、“行走”扩散和“跳跃”扩散，每一种扩散机制都受分子与网络的连通性控制。这些动力学模式结合在一起，导致了不同长度尺度上的多个自扩散区域，包括终端Fickian扩散之前的两个不同的表观超扩散区域，这与实验一致。这两种超扩散机制有不同的物理起源：一种是由于从步行到跳跃的转变，第二种是在较小的尺度上单独行走，即使没有跳跃也是如此。这第二个超扩散区域被认为是由于粘合剂分离时链扩散体积的增加，与结合形成的“笼子”相比，这增加了行走的步幅。由于其对行走和跳跃模式的影响，每个自扩散区域对粘合剂浓度、平衡常数和缔合/解离动力学都高度敏感。值得注意的是，增加链的贴纸密度会促进分子内环，并通过跳跃实现超扩散缩放；相反，增加链浓度会促进分子间结合并抑制跳跃，导致动力学在所有长度尺度上接近费克质心扩散的平均场极限。对跳跃和行走扩散系数的分析预测表明，静态网络结构、键寿命和每个动态模式的贡献之间存在联系，定性地与模拟一致。
Anomalous self-diffusive behavior in associative polymer gels has been attributed to the presence of multiple diffusive mechanisms on different length scales; however, the role of these dynamic modes in networks of linear polymers with pendant stickers remains unknown, particularly at sticker densities below the mean-field limit. Here, a generalized Brownian dynamics model is developed to study the effect of transient binding on self-diffusion of unentangled linear polymers with regularly spaced stickers, selected as a prototypical associative network model with wide experimental relevance. The simulations reveal an interplay between several diffusive mechanisms, including segmental fluctuations, “walking” diffusion, and “hopping” diffusion, each governed by a molecule’s connectivity to the network. These dynamic modes combine to result in multiple self-diffusive regimes on different length scales, including two distinct regimes of apparent superdiffusion before terminal Fickian diffusion, consistent with experiments. The two superdiffusive regimes have different physical origins: while one occurs due to a transition from walking to hopping, the second occurs from walking alone on smaller length scales, even in the absence of hopping. This second superdiffusive regime is proposed to arise from an increase in the chain pervaded volume upon sticker detachment, which increases the walking step size compared to the “cage” formed by binding. Each self-diffusive regime is highly sensitive to the sticker concentration, equilibrium constant, and association/dissociation kinetics due to their effects on the walking and hopping modes. Notably, increasing a chain’s sticker density promotes intramolecular loops and enables superdiffusive scaling through hopping; in contrast, increasing the chain concentration promotes intermolecular binding and suppresses hopping, resulting in dynamics approaching the mean-field limit of Fickian center-of-mass diffusion on all length scales. Analytical predictions for the hopping and walking diffusivities demonstrate a link between the static network structure, bond lifetime, and the contribution of each dynamic mode, with qualitative agreement with simulation.
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影响因子：
5.5
作者：
Shen, Wei;Kornfield, Julia A.;Tirrell, David A.
通讯作者：
Tirrell, David A.
影响因子：
5.5
作者：
Ramirez, Jorge;Dursch, Thomas J.;Olsen, Bradley D.
通讯作者：
Olsen, Bradley D.
影响因子：
5.5
作者：
Rasid, Irina Mahmad;Holten-Andersen, Niels;Olsen, Bradley D.
通讯作者：
Olsen, Bradley D.
具有多部分贴纸的瞬态遥爪网络的机械响应。
DOI：
10.1063/1.4993649
发表时间：
2017
期刊：
The Journal of chemical physics
影响因子：
--
作者：
M. K. Sing;Jorge Ramírez;B. Olsen
通讯作者：
B. Olsen
影响因子：
15
作者：
Rapp PB;Omar AK;Silverman BR;Wang ZG;Tirrell DA
通讯作者：
Tirrell DA